Dishwashers (or warewashers), particularly of the commercial variety, often include water-saving features to reduce water and energy consumption.
As an example, the Model C-44A series dishwashers available from Hobart Corporation include a wash tank divided into wash and rinse sections and housing a wash liquid (typically detergent charged water). Spray arms are disposed within each of the wash and rinse sections to spray wash liquid and rinse liquid (typically water), respectively, onto dishware. The sections are typically divided by a curtain and a divider plate to contain sprayed liquid within each section, although a space is typically provided below the divider plate to allow for the flow of liquid between the two sections of the wash tank. A conveyor system moves dishware between the sections.
All or most of the wash liquid sprayed on dishware within the wash section drains back into the wash tank to be reused. In addition, most of the rinse liquid sprayed on dishware within the rinse section also flows back into the wash tank and mixes with the wash liquid. However, a small rinse catch pan (about 50 to 80 square inches) is disposed within the rinse section to divert a portion of the rinse liquid to the drain.
While this system of returning a majority of the rinse liquid to the wash tank reduces overall water consumption, a greater concern is raised as to the consumption of detergent. In particular, the concentration of detergent in the wash liquid must be carefully controlled to provide optimum cleaning. However, the addition of rinse liquid has the effect of diluting the concentration of detergent in the wash liquid, thereby reducing the performance of the machine. Moreover, additional detergent must be added to the wash liquid (typically by an automatic closed-loop system) to maintain the proper concentration. As a result, it has been found that an excessive amount of detergent is used in these machines.
Over-use of detergent increases operating costs, as well as poses environmental concerns. Over-use of detergent also does not improve cleaning performance. Therefore, a substantial need has arisen for a manner of reducing detergent consumption in dishwashers and the like, while maintaining optimum dishwasher performance.